Corrosion inhibitor



United States Patent,

CORROSION INHIBITOR Roy A. Westlund, Jr., and Harry W. Rudel, Roselle, N.J., assignors to Esso Research and Engineering Company, a corporation of Delaware No Drawing. Application August 6, 1956 Serial No. 602,443

7 Claims. (Cl. 252-46.7)

to the equipment caused by the petroleum crude oils, the

vario'us intermediate hydrocarbon fractions of the crudes, and even the finished petroleum products. Crude oils are generally acidic in nature andalso contain sulfur coinpounds ranging from abofut0.03.%]forgPennsylvania crudes to about 5.0% in Mexican crudes.; Many of these various sulfur compounds break down into H 8 on heating in various stages of petroleum processing. The acidic materials and the H 8 are very corrosive to metal. Furthermore, crude oils and their various hydrocarbon fractions frequently contain a small amount of water which may have been initially present in the crude oil or which may have been added during various refining operations, such as steam stripping. The presence of water aggravates the corrosion problem, as water furnishes a medium for the acidic materials and sulfur compounds, thereby greatly increasing the degree of corrosivity. In general, the crude and various oil fractions at different stages of processing or storage may be considered as consisting of one or more of three phases; i.e., an oil phase, a wateroil phase, and a water phase. Of these three phases, encountered in refinery operations, the oil phaseand the water-oil phase are the least corrosive and generally are easily inhibited. The water phase, on the other hand, which might be present in pipelines, storage 'or distilling operations, is a serious contributor" to corrosion and is the most difficult to inhibit. A large number of various types of corrosion inhibitors have been proposed and are commercially available. However, it has been found that while most of these commercial inhibitors elfectively inhibit rusting in the oil and-water-oil phase, they have little eifect on the water phase and, in fact, they frequently increase corrosion in the water phase.

It has now been found that certain imidazolines, which have been phospho-sulfurized, will form an additive which greatly reduces corrosion in refinery equipment caused by sulfur compounds, such as H 8 and various acidic materials. This additive may be added directly to the crude or to any of the normally liquid petroleum fractions at any stage of processing, or to the finished product. Generally, the lighter petroleum fractions exhibit a higher degree of corrosion and it may be desirable to add the inhibitor only to these lighter fractions after the original distillationof the crude into its various fractions.

Generally, a concentration in the oily material of about I V 2. r much more corrosive than others. I Jsually, about 10 to p.p.m. of the inhibitor .will be used. The additive material left in the finished oil product and thereby furnishes protection againstxcorrosion during the life or the product. The additive has no undesirable effect on the finished product and does not interfere withthe addition of other additives to the final product.

The rust inhibitors of the invention, areJfofn-red by re- 'acting 1 mole of the imidazoline with from about 0.05

to 1.0 moles, e.g., 0.10'to 0.50 mole of a phosphorus sulfide compound; at temperatures of about 200 to "400 F.,

e.g., 300 to 350 F.; under an "inertatmosphere to prevent oxidation, such as a nitrogen blanket; for from aboutv 0.2 5:to 4.0 hours, e .g., 1.0 to 2.0 hours After the reaction is completed the reaction product is cooled to about 200 to 300 F,, and m ay be filtered to give a:-final I product which is useful as a corrosion inhibitor. 7

The imidazoline compounds useful in the invention are 6 carbon atoms. These imidazolines ,are readily pre pared by reacting the proper organic acid with a suitable hydroxyfsubstituted diamine. One such product which is. commercially available under the name Amine 220, is the reaction product of oleic acid and amino ethyl .ethanolamine, said reaction,

Another example of an imidazoline of the general formula is l-hydroxy ethyl, 2-(heptadecadieny1-8,1l) 2 imidazoline. I a

i in carryingout the phospho-sulfurization, any of the various phospho-sulfurization agents may be used, such as P285, P483 and P487.

The invention will be more fully understood by the following examples: v l

- EXAMPLE 1 1 0.667 mole bf l-hydroxy ethyl 2-(heptadecenyl-8) 2-imidazolineand 0.16 mole of P 8 were mixed at room 1 temperature was about 15.0 minutes.) The mixture was then cooled and filtered through filterpaper' at 300 and the product was further cooled to'r'oom temperature.

The product was a dark greenish liquid, almost black. The product of Example I was then tested for corro- -siori inhibiting propertiesin a test procedure designed to Patented Mar. 1, 1960- product having the 3 simulate the operation of a'pip'estill, as described in the following example.

EXAMPLE II The corrosion rate tests were carried out in sealed Carius tubes which were about "19 mm. ID. and about 70 cm. long. A mixture of 85 volume percent of a hydrocarbon fraction and 15 volume percent of water was placed in the tube, filling it to a level of about 42 cm. and providing an overhead vapor space of about 28 cm. The hydrocarbon fraction was a naphtha, commonly known as Stoddard Solvent, and having the following properties:

18 wt. percent aromatics 40 wt. percent .naphthenes 42 wt. percent ,paraffins 1 Boiling range, F 310-400 Specific gravity 60760 F. 0.790 Flash point, F. 107

Aniline point, F 129 The tubes are placed in steel jackets and the jackets placed in an oil bath maintained at 140 C. for a period of 18 hours. The tube is immersed in the bath to a depth of 17 cm. so that boiling takes place in the lower part of the tube and condensation occurs in the upper part of the tube. This gives a three phase system consisting of:

(1) Water phaseat the bottom of the tube.

(2) Mixed hydrocarbon-water phase-in the center section of the tube.

(3) Vapor phaseat the upper portion of the tube.

Weighed test coupons are placed in the appropriate phase and held by means of glass threads. In the water phase, the coupon is allowed to rest on the bottom of the tube. The coupons are prepared from a mild steel, of the type used in refinery equipment, and are cleaned by rinsing in acetone and then are grit-blasted to provide a fresh surface.

After placing the test specimens in position, the acidity of the medium was adjusted by the addition of HCl to a pH of 3, since it is known that pipestills operate under a pH of from about 2 to 6 or 7. Sufiicient H S was bubbled through the mixture until the concentration of H 8 was about 50 ppm. (parts per million). A suflicient amount of the inhibitor to be evaluated was added to the mixture to provide an inhibitor concentration of 50 p.p.m. The tube is sealed and heated as described for 18 hours. After exposure, the tube is cooled and opened and the test specimens reweighed.

The percent protection is calculated from the following formula:

Percent; protection loss of Wt. by blank loss of wt. of test specimen 100 loss of wt. by blank 1 The loss of wt. by the blank is determined by repeating the experiment with no inhibitor being present.

The above test was carried out on the product of Ex ample I. For comparison purposes a number of other inhibitors, including several commercial inhibitors, were also tested by the above method.

The results showed that all the inhibitors tested gave excellent protection (better than 95%) in the mixed hydrocarbon-water phase. None of the inhibitors was eflective in the vapor phase, due to the extremely low volatility of the inhibitors. In actual practice, protection of the vapor layer from overhead corrosion is effected by the use of volatile inhibitors such as ammonia or low molecular weight amines. "These are well known inhibitors but due to their 'high volatility, they do not afford any protection to the lower layers, particularly the water phase. On the other hand, inhibition of the water phase is extremely dilficult and it is with this .phase that the invention is particularly concerned. The usefulness of the compounds of this invention in reducin'g corrosion of the water phase is showntin the following table.

Table 1.--Corr0sion inhibiting properties of 50 p.p.m. of inhibitor in naphtha Percent Proteclnhibitor tion Water Layer H|N(CHr-CHr-NH)s-GHr-OHr-NH: 3. 5 CmHar-(N -O z-CH2)D-N H l. 9

H OuHar-(NHF-OHECFB)N-C;Haa -52. 0

HgN(CHgCHg-NH)g-CHg-CHr-NH5 l. 9 Polyrad 1110 1 156. 0

'E H a w z-fil z)ofi fircflalr ei z-c fih (Where 12:04, 0 or Oualkylgroup) :-152. 0

Product 0! Example'I 2 56. 5

1 Commercial inhibitor which is the condensationproduct of rosin amine and ethylene oxide.

Reaction product of P285 and l-hydroxyethyl, 2-heptadeceny1-8, 2-imidazoiine.

As seen from the above table, the product of theinvention gave 56.5% protection in the water la'yer int 50 parts per million concentration. The otherjcompounds tested, some of which are commercial inhibitors, actually increased corrosion in the water layer as "indicated by the minus signs.

What is claimed is:

1. As a compound adapted .to inhibit corrosion, the reaction product of 0.10 to 0.50 mole of a phosphorus sulfide and 1 mole of an .imidazoline having the generalformula:

wherein R .issel'ected from the group consisting of alkyl and alkylene radicals containing .fromabout 210 22 carbon atoms and R is a substituent selected from the group consisting of hydrogen and alkyl radicals containing 1 to 6 carbon atoms,wherein saidreaction is carried out at a temperature of about 200 to 400 F. .for about 0.25 to 5.0 hours under an inert atmosphere.

2. As a corrosion inhibitor the xeaction product of 0.05 to 1.0 mole of a phosphorus sulfide, and 1 mole of an imidazoline having the general formula:

0.25 to 5.0 hours under an inert atmosphere.

3. As a corrosion inhibitor, the reactionproduct of J an" 0.10 to 0.50 mole of a phosphorus sulfide and 1 mole of an imidazoline having the general formula:

wherein R is selected from the group consisting of alkyl and alkylene radicals containing about 10 to 20 carbon atoms and R is a substituent selected from the group consisting of hydrogen and alkyl radicals containing 1 to 6 carbon atoms, said reaction being carried out at a temperature of about 300 F. to 350 F. for about 1.0 to 2.0 hours, under an inert atmosphere.

4. A petroleum hydrocarbon containing as. a corrosion inhibitor, from about 5 to 200 parts per million of the reaction products of 0.05 to 1.0 mole of a phosphorus sulfide and 1 mole of an imidazoline having the general formula:

( JHCHmH ll. wherein R is selected from the group consisting of alkyl and alkylene radicals containing from about 2 to 22 carbon atoms and R is a substituent selected from the group consisting of hydrogen and alkyl radicals containing 1 to 6 carbon atoms, wherein said reaction is carried out at a temperature of about 200 to 400 F. for about 0.25 to 5.0 hours under an inert atmosphere.

5. A method of inhibiting corrosion of steel in contact with a petroleum hydrocarbon fraction which comprises adding to said hydrocarbon fraction about 5 to 200 parts per million of a corrosion inhibitor which is the reaction product of 0.5 to 1.0 mole of a phosphorus sulfide and 1 mole of an imidazoline having the general formula:

wherein R is selected from the group consisting of alkyl and alkylene radicals containing from about 2 to 22 carbon atoms, and R is a substituent selected from the group consisting of hydrogen and alkyl radicals containing 1 to 6 carbon atoms, wherein said reaction is carried out at a temperature of about 200 to 400 F. for about Y 0.25 to 5.0 hours under an inert atmosphere.

6. A method of inhibiting corrosion of steel in contact with a petroleum hydrocarbon fraction containing a trace of water which comprises adding to said hydrocarbon fraction about 5 to 200 parts per million of a corrosion inhibitor which is the reaction product of 0.05 to 1.0 mole of a phosphorus sulfide, and 1 mole of an imidazoline having the general formula: I l

and alkylene radicals containing from about 2 to 22 carbon atoms and R is a substituent selected from the group consisting of hydrogen and alkyl radicals, containing 1 to 6 carbon atoms, said reaction being carried out at a temperature of about 200 to 400 F. for about 0.25 to 5.0 hours under an inert atmosphere.

7. A process for preparing a phosphorus sulfurized imidazoline which comprises reacting about 0.05 to 1.0 mole of a phosphorus sulfide per mole of imidazoline having the general formula:

(ilHCHrOH wherein R, is selected from the group consistingof alkyl and alkylene radicals containing from about 2 to 22 carbon atoms and R is a substituent selected from the group consisting of hydrogen and alkyl radicals containing 1 to 6 carbon atoms, said reaction being carried out at a temperature of about 200 to 400 F. for a time of about 0.25 to 5.0 hours, under an inert atmosphere, and recovering a reaction product therefrom.

References Citedin the file of this patent UNITED STATES PATENTS 

2. AS A CORROSION INHIBITOR THE REACTION PRODUCT OF 0.05 TO 1.0 MOLE OF A PHOSPHORUS SULFIDE, AND 1 MOLE OF AN IMIDAZOLINE HAVING THE GENERAL FORMULA:
 4. A PETROLEUM HYDROCARBON CONTAINING AS A CORROSION INHIBITOR, FROM ABOUT 5 TO 200 PARTS PER MILLION OF THE REACTION PRODUCTS OF 0.05 TO 1.0 MOLE OF A PHOSPHORUS SULFIDE AND 1 MOLE OF AN IMIDAZOLINE HAVING THE GENERAL FORMULA: 